Carboxyphosphonate brush control agents

ABSTRACT

Carboxyphosphonates such as trisodium carboxyphosphonate are useful for regulation of plant growth.

RELATED APPLICATIONS

This is a division of application Ser. No. 769,096 filed Feb. 16, 1977,which is a division of Ser. No. 590,374, filed June 25, 1975, now U.S.Pat. No. 4,018,854, which is a division of Ser. No. 474,537, filed May30, 1974, now abandoned which is a continuation-in-part of my earlierfiled application U.S. Ser. No. 381,619, filed July 23, 1973, abandoned.

BACKGROUND OF THE INVENTION

This invention relates to carboxyphosphonates and their use as brushcontrol agents. The use of various carbamoylphosphonates for control ofplant growth is known in the art. For example, U.S. Pat. No. 3,627,507and Offenlegungsschrift No. 2,040,367 relate to the use ofcarbamoylphosphonates for plant growth control. However, neither ofthese references suggest the carboxyphosphonates of this invention.Berichte 57, 1023 (1924) describes trisodium carboxyphosphonate as wellas the zinc, manganese, copper, lead and silver salts. However, thisreference does not describe any utility for these salts.

SUMMARY OF THE INVENTION

Plant growth can be regulated by application to the plants of compoundsof the formula ##STR1## wherein M is selected from sodium, lithium,potassium, calcium, magnesium, zinc, manganese, barium or ##STR2## R isM, alkyl of 1 to 8 carbons, optionally substituted with a chlorine, abromine, a fluorine, or an iodine atom; alkenyl of 3 to 8 carbon atoms,##STR3## WHERE A is chlorine or methyl, B is chlorine or methyl, n is 0or 1, and m is 0 or 1;

R₁ is hydrogen, alkyl of 1 to 4 carbon atoms, or hydroxyalkyl of 2 to 4carbon atoms;

R₂ is hydrogen, alkyl of 1 to 4 carbon atoms, or hydroxyalkyl of 2 to 4carbon atoms;

R₃ is hydrogen, alkyl of 1 to 4 carbon atoms, of hydroxyalkyl of 2 to 4carbon atoms; and

R₄ is hydrogen or alkyl of 1 to 12 carbon atoms, provided that the totalnumber of carbon atoms in R₁, R₂, R₃ and R₄ is less than 16.

Of these compounds, those wherein R is alkyl of 1 to 4 carbon atoms or Mwhere M is sodium or potassium are preferred. Within this grouppreferred compounds are trisodium carboxyphosphonate, disodium ethylcarboxyphosphonate, and disodium methyl carboxyphosphonate.

The active compounds described above can be applied to plants toregulate plant growth. The phrase "applied to plants" as used hereinincludes both direct application to the plants and also application tothe soil in which the plants grow.

Of the compounds described above, those where M is limited to lithium,potassium, calcium, magnesium, barium or ##STR4## and R is M or alkyl of1 to 8 carbon atoms, optionally substituted with a chlorine, bromine,fluorine or iodine atom; alkenyl of 3 to 8 atoms; or ##STR5## where A ischlorine or methyl and B is chlorine or methyl; n is 0 or 1; m is 0 or1, are novel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compounds useful in this invention are formed by alkaline hydrolysisof the appropriately substituted alkyl carboxyphosphonate. Thehydrolysis is conducted by refluxing the starting material in aqueoussolutions having 2 or 3 equivalents of alkali metal hydroxide. Once analkali metal salt is formed, other salts can be formed by reaction withmetal salts of other acids or by conventional ion exchange. It should benoted that the activity of the compounds useful in this inventionresides in the carboxyphosphonate anion. The exact identity of thecations with which it is associated is of little significance. Thepreparation of the compounds of this invention is further illustrated bythe following examples.

EXAMPLE 1

Using the method of Nylen, Ber., 57B, 1023 (1924), a solution of 21parts ot triethyl carboxyphosphonate in 60 parts of water containing 24parts of 50% sodium hydroxide was refluxed for 2 hrs. The solution wasallowed to cool overnight. Filtration of the reaction mixture gave 4.7parts of the product, trisodium carboxyphosphonate hexahydrate,mp >250°; ν_(KBr) = 1560, 1530 cm⁻¹.

In a similar manner, by using the appropriate metal hydroxide, thefollowing compounds can be prepared:

    ______________________________________                                         ##STR6##                                                                     (R is M)                                                                      ______________________________________                                        Li                                                                            Ca                                                                            Mg                                                                            Zn                                                                            Mn                                                                            Ba                                                                            ______________________________________                                    

The triammonium salts cannot be prepared directly by hydrolysis of thetrialkyl esters. They must be obtained by passage of a solutioncontaining trisodium carboxyphosphonate through an ion exchange columnpreviously treated with the appropriate ammonium cation.

In such a manner, the following compounds can be prepared:

    ______________________________________                                                  ##STR7##                                                                     M                                                                    ______________________________________                                                 NH.sub.4                                                                      (CH.sub.3)NH.sub.3                                                            (C.sub.4 H.sub.9)NH.sub.3                                                     (C.sub.12 H.sub.25)NH.sub.3                                                   (CH.sub.3).sub.2 NH.sub.2                                                     (CH.sub.3)NH.sub.2 (C.sub.12 H.sub.25)                                        (CH.sub.3).sub.3 NH                                                           (C.sub.4 H.sub.9).sub.3 NH                                                    (CH.sub.3).sub.4 N                                                            (CH.sub.3).sub.3 N(C.sub.4 H.sub.9)                                           (CH.sub.3).sub.3 N(C.sub.12 H.sub.25)                                         (C.sub.2 H.sub.4 OH)NH.sub.3                                                  (HOCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2)NH.sub.3                               (CH.sub.3)NH.sub.2 (CH.sub.2 CH.sub.2 OH)                                     (CH.sub.3)N(CH.sub.2 CH.sub.2 OH).sub.3                              ______________________________________                                    

EXAMPLE 2

A solution of 15.5 parts of ammonium ethyl carbamoylphosphonate and 16parts of 50% sodium hydroxide in 50 parts of water was refluxed for 2hours. The solution was cooled and evaporated under vacuum to dryness togive the disodium ethyl carboxyphosphonate, m.p. >300°, ν_(neat) = 1580(C═O), 1080 (P--O⁻), 1040 (P--OCH₂ CH₃) cm⁻¹.

EXAMPLE 3

To a solution of 8.5 parts of trimethyl carboxyphosphonate in 50 partsof water was added slowly 8.0 parts of 50% sodium hydroxide. Thesolution was refluxed for 1 hour, cooled and the solvent removed undervacuum to give 10.6 parts of disodium methyl carboxyphosphonate,m.p. >250°, ν_(neat) = 1580, 1080 (P--O³¹), 1050 (P--OCH₃)cm⁻¹.

In a similar manner, by using the appropriate metal hydroxide andphosphonate ester, the following compounds can be prepared:

    __________________________________________________________________________     ##STR8##                                                                     R                     M  m.p.                                                                              ν Neat (PO.sup.⊖)                     __________________________________________________________________________    CH.sub.2CHCH.sub.2    Na > 300°                                                                     1100 cm.sup.-1                                   CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2                                                                 Na > 300°                                                                     1105 cm.sup.-1                                   C.sub.6 H.sub.5 CH.sub.2                                                                            Na > 300°                                                                     1100 cm.sup.-1                                   CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                               Na --                                                   CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                               K  --                                                   CH.sub.2CHCH.sub.2    Li --                                                    ##STR9##             Ca --                                                   ClCH.sub.2 CH.sub.2   Mg --                                                    ##STR10##            Zn --                                                   CH.sub.2CHCH.sub.2 CH.sub.2                                                                         Mn --                                                   CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2                                                                 Ba                                                      BrCH.sub.2 CH.sub.2   Na                                                      FCH.sub.2 CH.sub.2    Na                                                      ICH.sub.2 CH.sub. 2   Na                                                       ##STR11##            Na                                                       ##STR12##            Na                                                       ##STR13##            K                                                       CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2CHCHCH.sub.2                                            Na                                                      __________________________________________________________________________

By passage of a solution of an appropriate disodium alkylcarboxyphosphonate through an appropriate ion exchange column;pretreated with the appropriate ammonium cation, the following compoundscan be prepared:

    ______________________________________                                         ##STR14##                                                                    R                  M                                                          ______________________________________                                        CH.sub.3           NH.sub.4                                                   CH.sub.3 CH.sub.2  NH.sub.4                                                   CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2                                                              (CH.sub.3)NH.sub.3                                         CH.sub.2CHCH.sub.2 (C.sub.4 H.sub.9)NH.sub.3                                  CH.sub.3 CH.sub.2  (C.sub.12 H.sub.25)NH.sub.3                                 ##STR15##         (CH.sub.3).sub.2 NH.sub.2                                  ClCH.sub.2 CH.sub.2                                                                              (CH.sub.3)NH.sub.2 (CH.sub.2 CH.sub.2 OH)                   ##STR16##         (C.sub.4 H.sub.9).sub.2 NH.sub.2                           CH.sub.3           (CH.sub.3).sub.3 NH                                        CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2                                                              (C.sub.4 H.sub.9).sub.3 NH                                 CH.sub.3 CH.sub.2  (HOCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2).sub.3 NH           CH.sub.3 CH.sub.2  (CH.sub.3).sub.4 N                                         CH.sub.2CHCH.sub.2 CH.sub.2                                                                      (CH.sub.3).sub.3 N(C.sub.12 H.sub.25)                      CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                            NH.sub.4                                                   CH.sub.3 CH.sub.2 CH.sub. 2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                         (CH.sub.3)NH.sub.3                                         ______________________________________                                    

The compounds of this invention are useful for controlling the growth ofplants. The compounds of this invention are particularly useful forpreventing bud break and retarding the growth of woody plants. Thus, thecompounds of this invention can be applied in areas such as power linerights-of-way where low-growing and slow-growing vegetation isespecially desirable.

In addition to their value as plant growth retardants, the compounds ofthis invention can also be used to control flowering, fruit set, andcoloration on apples and other fruits. They are useful in controllingthe growth and flowering of ornamental species such as chrysanthemum andazalea.

The compounds of this invention can also be used to prolong the dormancyof perennial plants, and thereby protect the unsprouted buds from frostdamage. This can be especially important in the protection of flowerbuds, which in some years may sprout early and be killed by coldtemperatures. Application to plants in the stage where the next year'sbuds are being initiated, or are developing gives marked retardation ofbud break the following spring and greatly reduced growth.

To illustrate the growth-retardant activity of the compounds of thiscase, the following data are presented.

In one test, the test compound was applied in a solvent with a wettingagent and a humectant to cotton plants (five-leaf stage includingcotyledons), bush bean (second trifoliate leaf expanding), morningglory(four-leaf stage including cotyledons), cocklebur (Xanthium sp.,four-leaf stage including cotyledons), Cassia tora (three leavesincluding cotyledons), nutsedge (Cyperus rotundus, three to five-leafstage), crabgrass (Digitaria sp., two-leaf stage), barnyardgrass(Echinochloa sp., two-leaf stage), wild oats (Avena fatua, one-leafstage), wheat (two-leaf stage), corn (three-leaf stage), soybean (twocotyledons), rice (two-leaf stage), and sorghum (three-leaf stage).

Treated plants and controls were maintained in a greenhouse for 16 days,then all species were compared with controls and visually rated forresponse to treatment.

    __________________________________________________________________________    POST EMERGENCE                                                                                     morn-             barn-                                              Kg/                                                                              bush                                                                             cot-                                                                             ing cock-                                                                             cas-                                                                             nut-                                                                              crab-                                                                            yard                                                                              wild      soy-  sor-               Compound    Ha bean                                                                             ton                                                                              glory                                                                             lebur                                                                             sia                                                                              sedge                                                                             grass                                                                            grass                                                                             oats                                                                             wheat                                                                             corn                                                                             bean                                                                             rice                                                                             ghum               __________________________________________________________________________     ##STR17##  2  2C 10P                                                                           9G 2H                                                                            7C  6G 2C                                                                             7C 0   0  7G 3C                                                                             0  0   7G 5U                                                                            9P 5I                                                                            0  7G 3U               ##STR18##  2  8G 8Q 2H                                                                         8G 2H                                                                            8G  0   0  0   0  0   0  0   5G 1U                                                                            0  2G 7G 2U               ##STR19##  2  9C 9D                                                                            9G 3C                                                                            7C  2G  5G 0   6G 8G 3C                                                                             6G 2C                                                                            6G 1C                                                                             7G 1C                                                                            10P                                                                              1C 7G 1C               ##STR20##  2  9D 7C                                                                            6G 1C                                                                            8C  2G  5G 0   5G 8C  3G 5G  7G 1C                                                                            6G 5G 7G                  ##STR21##  2  9G 6Y                                                                            5G 4G  2G  0  0   2G 2C 7G                                                                             2G 2G  1C 7G                                                                            9P 6G 7G                 __________________________________________________________________________

In another test, the test compound was applied in a similar solvent topots of privet (Ligustrum sp.), willow (Salix sp.), forsythia (Forsythiasp.), Arbor Vitae (Thuja sp.), and apple (Malus sp.). The plants weremaintained in a greenhouse. Plant response ratings were taken 1 week and4 weeks after application.

    __________________________________________________________________________             Application                  Arbor                                            Rate   Privet Willow  Forsythia                                                                            Vitae  Apple                            Compound Kg./hectare                                                                          1 wk                                                                             4 wks                                                                             1 wk                                                                              4 wks                                                                             1 wk                                                                             4 wks                                                                             1 wk                                                                             4 wks                                                                             1 wk                                                                             4 wks                         __________________________________________________________________________     ##STR22##                                                                             2.2 0.6                                                                              0 0                                                                              5G 0                                                                              0 0 8G 5X 5X                                                                          0 0                                                                              10G 10G                                                                           0 0                                                                              0 0 0 0                                                                              6G 0                          __________________________________________________________________________

In a third test, the test compound was applied in a similar solvent topots of Black Valentine bean (Phaseolus vulgaris cv. Black Valentine),apple (Malus sp.) and willow (Salix sp.). The plants were maintained ina greenhouse, and plant response ratings were taken after application asindicated.

    __________________________________________________________________________                   B.V. Bean                                                                              Apple   Willow                                                  Rate 1   4    1   4   1   4                                         IN #      Kg/Ha                                                                              week                                                                              weeks                                                                              week                                                                              weeks                                                                             week                                                                              weeks                                     __________________________________________________________________________     ##STR23##                                                                              1    9G  10C  0   6G 3X                                                                             7G  6G 5X                                     -Na.sup.+ 4    9G  10C  0   10G 10G 9G 5X                                     __________________________________________________________________________

The plant response ratings (above) are composed of a number and aletter. The number describes the extent of the response and ranges fromzero to 10 with zero representing no response, and 10 representing 100%response. The letter describes the type of the response, as follows:

C, chlorosis-necrosis; H, formative effect (Malformation;

D, defoliation; U, unusual pigmentation;

G, growth retarded; I, increased chlorophyll;

P, terminal bud injury; 8Q*, increased fruit size;

X, axillary stimulation, 8Y*, Abscised buds or flowers *Note: With the"8Q" and "6Y", the number does not refer to extent of response (anypercent increase in fruit size is represented by an 8Q.

The term "plant growth retardant" as used in this disclosure is to beunderstood to mean an agent which, when applied to a plant or itsenvirons, will slow the growth of the plant. This also includes adelaying response on bud sprouting or prolonging of the dormancy period.

The compounds of this invention can be applied as foliar sprays or assoil applications to retard the growth rate of such plants or to affectflowering and fruit set.

Preferably, the compounds of this invention are applied as foliar ordormant wood sprays to the point of runoff although lower-volumeapplication can also be effective.

The compounds of the invention are very versatile and may be applied atone of many different time periods to suit the convenience of theapplicator. For example they may be applied in Spring a short time priorto the period when maximum plant growth is anticipated, to effect growthretardation. They may be applied later in the growing season just aftertrimming, to effect growth retardation. Or they may be applied when theyear's growth has ceased (late Summer, Fall, or Winter) with the resultthat treated plants will remain dormant the following Spring, whereasuntreated plants will sprout and grow. If flowering and fruit set are tobe modified, the treatment is applied before, during, or shortly afterflowering.

It will be recognized that the application rate is dependent upon thespecies to be treated and the results desired. In general, rates of from0.25 to 20 kilograms per hectare are used although higher or lower ratescan achieve the desired effect in some instances.

Useful formulations of the compounds of this invention can be preparedin conventional ways. They include dusts, granules, pellets, solutions,suspensions, emulsions, wetting powders, emulsifiable concentrates andthe like. Many of these may be applied directly. Sprayable formulationscan be extended in suitable media and used at spray volumes of from afew pints to several hundred gallons per acre. High strengthcompositions are primarily used as intermediates for furtherformulation. The formulations, broadly, contain about 1% to 99% byweight of active ingredient(s) and at least one of (a) about 0.1% to 20%surfactant(s) and (b) about 5% to 99% solid or liquid diluent(s). Morespecifically, they will contain these ingredients in the followingapproximate proportions:

    ______________________________________                                                  Active  Percent by Weight                                                     Ingredient                                                                            Diluent(s) Surfactant(s)                                    ______________________________________                                        Wettable Powders                                                                          20-90      0-74      1-10                                         Oil Suspensions                                                                            5-50     40-95      0-15                                          and Emulsions                                                                Aqueous Solutions                                                                         10-50     50-90      0-20                                         Dusts        1-25     70-99      0-5                                          Granules and                                                                               1-95      5-99      0-15                                          Pellets                                                                      High Strength                                                                             90-99      0-10      0-2                                           Compositions                                                                 ______________________________________                                    

Lower or higher levels of active ingredient can, of course, be presentdepending on the intended use and the physical properties of thecompound. Higher ratios of surfactant to active ingredient are sometimesdesirable, and are achieved by incorporation into the formulation or bytank mixing. Likewise, high levels of oils or humectants can beincorporated either in the formulation or by tank-mixing.

Typical solid diluents are described in Watkins, et al., "Handbook ofInsecticide Dust Diluents and Carriers", 2nd. Edn., Dorland Books,Caldwell, N.J. The more absorptive diluents are preferred for wettablepowders and the denser ones for dusts. Typical liquid diluents andsolvents are described in Marsden, "Solvents Guide", 2nd. Edn.,Interscience, New York, 1950. Solubility under 0.1% is preferred forsuspension concentrates; solution concentrates are preferably stableagainst phase separation at 0° C. "McCutcheon's Detergents andEmulsifiers Annual", Allured Publ. Corp., Ridgewood, New Jersey, as wellas Sisely and Wood, "Encyclopedia of Surface Active Agents", ChemicalPubl. Co., Inc., New York, 1964, list surfactants and recommended uses.All formulations can contain minor amounts of additives to reduce foam,caking, corrosion, microbiological growth, etc. Preferably, ingredientsshould be approved by the U.S. Environmental Protection Agency for theuse intended.

The methods of making such compositions are well known. Solutions areprepared by simply mixing the ingredients. Fine solid compositions aremade by blending, and, usually, grinding as in a hammer or fluid energymill. Suspensions are prepared by wet milling (see, for example,Littler, U.S. Pat. No. 3,060,084). Granules and pellets may be made byspraying the active material upon preformed granular carriers or byagglomeration techniques. See J. E. Browning, "Agglomeration", ChemicalEngineering, Dec. 4, 1967, pp. 147ff. and Perry's Chemical Engineer'sHandbook", 4th. Edn., McGraw-Hill, N.Y. 1963, pp. 8-59ff.

For further information regarding the art of formulation, see forexample:

H. m. loux, U.S. Pat. No. 3,235,361, Feb. 15, 1966, Col. 6, Line 16through Col. 7, Line 19 and Examples 10 through 41.

W. p. langsdorf, U.S. Pat. No. 3,627,507, Dec. 14, 1971. col. 8, line 1through col. 11, line 12 and Examples 60-65.

G. c. klingman, "Weed Control as a Science", John Wiley & Sons, Inc.,New York, 1961 pp. 81-96.

J. d. fryer and S. A. Evans, "Weed Control Handbook", 5th Edn. BlackwellScientific Publications, Oxford, 1968, pp. 101-103.

The following Examples further illustrate the formulation andapplication of the compounds of this invention.

EXAMPLE 4 Wettable Powder

disodium methyl carboxyphosphonate 40%

dioctyl sodium sulfosuccinate 1.5%

sodium ligninsulfonate 3%

low viscosity methyl cellulose 1.5%

attapulgite 54%

The ingredients are thoroughly blended, passed through an air mill, toproduce an average particle size under 15 microns, reblended, and siftedthrough a U.S.S. No. 50 sieve (0.3 mm opening) before packaging.

All compounds of this invention may be formulated in the same manner.

Fifteen kilograms of this formulation are mixed with 600 liters of waterin a sprayer fitted with an agitator. The mixture is sprayed on a 1hectare area of newly trimmed hedgerow in the spring after the leaveshave expanded. (The spray may be either directly on the plants or to thelocus of the plants.) This treatment greatly reduces the growth ofplants growing in the hedgerow, but does not seriously injure them.Thus, the hedgerow is kept neat with a minimum of labor expended fortrimming it.

EXAMPLE 5 Water-Soluble Powder

disodium ethyl carboxyphosphonate 95.0%

dioctyl sodium sulfosuccinate 0.5%

sodium ligninsulfonate 1.0%

synthetic fine silica 3.5%

The ingredients are blended and coarsely ground in a hammer mill so thatonly a few percent of the active exceeds 250 microns (U.S.S. No. 60sieve) in size. When added to water with stirring, the coarse powderinitially disperses and then the active ingredient dissolves so that nofurther stirring is needed during application.

Ten kilograms of this formulation are dissolved in 800 liters of watercontaining 0.5% of a non-phytotoxic wetting agent. This formulation issprayed from a helicopter to a 1 hectare area under an electric powerline in which the brush and trees have been freshly trimmed. Thistreatment retards the growth of black willow (Salix nigra), black cherry(Prunus serotina), and many other woody species.

EXAMPLE 6 Solution

trisodium carboxyphosphonate 12.5%

octylphenoxypolyethoxyethanol 0.5%

water 87.5%

The ingredients are combined and stirred to produce a solution which canbe applied directly or after dilution with additional water.

Fifteen liters of this solution are mixed with 200 liters of water andsprayed in late summer on a 1 hectare area of woody plants growing on apower line right-of-way. The treated plants continue to appear likeuntreated plants. However, the following year the treated plants remaindormant for an extremely long period of time, whereas untreated onessprout and grow normally. Thus, the treatment greatly reduces the amountof labor required to maintain the plants at a desirable height.

EXAMPLE 7 Oil Suspension

trisodium carboxyphosphonate 25%

polyoxyethylene sorbitol hexaoleate 5%

highly aliphatic hydrocarbon oil 70%

The ingredients are ground together in a sand mill until the solidparticles have been reduced to under about 5 microns. The resultingthick suspension may be applied directly, but preferably after beingextended with oils or emulsified in water.

One part of this suspension is mixed with one part of water in a sprayerfitted with an agitator, and applied in winter to the point of runoff onthe bark of dormant woody plants growing under a power line. The treatedplants remain dormant for an extremely long period of time, thus greatlyreducing plant growth and also the labor required for pruning.

I claim:
 1. A method of retarding the growth of plants which consistsessentially of applying to the plants an effective amount of a compoundof the formula ##STR24## wherein M is sodium, lithium, potassium,calcium, magnesium or barium, or ##STR25## R is M; R₁ is hydrogen, alkylof 1 to 4 carbon atoms, or hydroxyalkyl of 2 to 4 carbon atoms;R₂ ishydrogen, alkyl of 1 to 4 carbon atoms, or hydroxyalkyl of 2 to 4 carbonatoms; R₃ is hydrogen, alkyl of 1 to 4 carbon atoms, or hydroxyalkyl of2 to 4 carbon atoms; R₄ is hydrogen or alkyl of 1 to 12 carbon atoms,provided that the total number of carbon atoms in R₁, R₂, R₃ and R₄ isless than
 16. 2. The method of claim 1 wherein M is sodium.